C4U

Arithmetic micro-operations constitute two varieties of among of which, one are BASIC Arithmetic Micro-operations and second are DERIVED Arithmetic Micro-operations.

Simple operations like ADDITION, SUBTRACTION, COMPLEMENTATION etc. are considered as BASIC micro-operations while MULTIPLICATION and DIVISION are the operations that undergo DERIVED Micro-operations.

A Multi-bit binary adder is simply a series of â€œnâ€�, 1-bit full adders cascaded together with each full adder representing a single weighted column in a long binary addition. It is often called a ripple carry adder because the carry signals produce a â€œrippleâ€� effect through the binary adder from right to left, (LSB to MSB).

A multi-bit adder-subtractor uses the same circuit of cascaded FULL ADDERS. This circuit adds in the same way as the multi-bit adder, but subtracts using the twos complement method.

When subtraction is required, the C_{0} is set to logic 1, which causes the bit at any particular B input to be complemented by an XOR gate before being fed to input B of the full adder circuit.

The binary incrementer increases the value stored in a register by â€˜1â€™. For this, it simply adds â€˜1â€™ to the existing value stored in a register. It is made by cascading â€˜nâ€™ half adders for â€˜nâ€™ number of bits i.e. the storage capacity of the register to be incremented. Hence, a 4-bit binary incrementer requires 4 cascaded half adder circuits.